1. Field of the Invention
The present invention relates to automotive boots and, more particularly, to a boot having a fixed end and a floating end to seal an encircled element against foreign matter while accommodating axial translation and limited rotational and pivotal movement between the fixed and floating ends.
2. Description of the Prior Art
Tube like flexible boots have been used in various automotive, industrial and other applications to protect extensible members from environmental contaminants. Often, the extensible members effect a combination of axial and rotational movements between the elements to which they are attached. In such prior applications, both ends of the boot may be fixedly attached to the respective encircled shaft and housing to form a seal. Similarly, boots used to protect the junction between telescoping members where there is no relative rotational or pivotal movement between the members, may be fixedly secured at both ends. However, when both ends of a boot are fixedly secured to two elements which reciprocally rotate with respect to one another, substantial twisting stresses are imposed upon the boot and its lifespan is a function of the ability of the boot material to withstand the stresses imposed. When there is compression and expansion of the boot in combination with a twisting motion, the boot will fatigue more rapidly or not function at all. A boot split or torn as a result of fatigue induced non compliance will expose the protected elements to foreign matter and thus defeat the purpose for which a boot was installed. Such exposure will quickly cause corrosion and damage with a possible resulting failure of the elements and jeopardy to operability of the vehicle. These problems are particularly prevalent in automotive applications in general and for MacPherson struts in particular.
Various mechanisms have been developed in an attempt to float one end of a boot to accommodate relative rotational and pivotal movement between the points of attachment of the ends of the boot. In one embodiment of a boot, a radially inwardly oriented channel is formed in a floating end of the boot for receiving the edge of a disk like element. To accommodate rotation, the channel must be in sufficiently loose engagement with the disk to permit rotation of the boot about the disk and avoid translation of twisting forces upon the boot. In practice, it has been found that to avoid twisting sufficient looseness of the fit must exist which fit will permit particulate matter and liquids to enter the boot through the floating end. In another embodiment, one end of the boot is rigidly secured to a collar. The collar includes a radially inwardly oriented channel for receiving an annular ridge in sliding engagement. To prevent unwanted restraint of rotational movement of the channel relative to the ridge, a substantial space therebetween must be provided, which space is also sufficient to prevent a substantial inflow of particulate matter and liquid into the boot. Modified versions of such radially inwardly oriented channels cooperating with radially extending ridges or disks have also been employed. In each of such configurations, a common problem is present. A certain amount of radially oriented space must exist to permit sufficient segregation and lack of frictional resistance to permit independent rotation therebetween. Since the radial width of this space is a function of the sealing capability of the interconnection, a dichotomy exists. Either the radial space must be sufficient to permit independent relative rotation between the parts, in which case an inflow of particulate matter and liquid occurs or the radial space must be minute enough to provide a seal against intrusion of particulate matter and liquids, in which case independent relative rotation between parts is inhibited. Furthermore, looseness of the fit will be noisy during operation of the vehicle, which noise is unacceptable. A further ongoing problem with boot designs in general is that of providing a means for air outflow and inflow as the boot compresses and extends.